In the solar energy radiations, infrared radiation (ray) is most closely related to heat. The infrared rays can be classified into near infrared rays and far infrared rays. The near infrared rays are directly transmitted to the Earth from the Sun, and the far infrared rays include heat which is generated from various heating apparatus. The infra red ray has a longer wavelength than visible rays, and easily penetrates a material which blocks the visible rays. Accordingly, filters for blocking the near infrared rays are conventionally used for an automobile glass or an architectural glass for preventing the near infrared rays from being excessively transmitted into the interior of an automobile or a building.
Also, in a plasma display panel (PDP) which is recently developed for providing a large-size screen, electrodes for supplying signals and power are formed on the front glass panel of the PDP. Thus, during the operation of PDP, a lot of electromagnetic waves and a lot of near infrared rays are generated at the glass panel. The generated near infrared rays may induce mis-operations of a remote controller or an infrared ray communication port which utilizes infrared rays for data transmissions. Therefore, the filters for blocking the near infrared rays are conventionally used for the glass panel of the PDP.
Generally, a near infrared ray absorption film can be produced by coating the mixture of a near infrared ray absorption dye and a binder resin on a transparent film. The filter for blocking the near infrared ray (i.e. near infrared ray filter) can be produced by stacking several near infrared ray absorption films on a glass. The near infrared ray absorption film should have a good durability at high temperature or at high humidity atmosphere, and also should have a good light absorptivity at the wavelength of 800-1200 nm (near infrared ray region). The durability of the near infrared absorption film is determined by the difference between the first transmittance of a new absorption film and the second transmittance of the absorption film after exposing the absorption film during a predetermined time interval under the condition of high temperature or high humidity atmosphere. As the difference is smaller, the durability of the near infrared absorption film is better. The durability of the near infrared absorption film depends on the kinds of binder resin and the dye.
Conventionally, organic dyes, such as ammonium, aminium, diimmonium, quinone, phthalocyanine, naphthalocyanine, cyanine, and so on, are used for producing the near infrared ray absorption film. However, the conventional organic dyes, when used alone, have a weak durability to heat or light. Therefore, in Korean Patent No. 10-497149, a dithiol based metal complex dye having a good thermal stability is added to the conventional organic dye. However, the dithiol based metal complex dye is harmful to a human body since the metal complex dye contains heavy metals such as nickel, and the metal complex dye is not compatible with some organic dyes. In Korean Patent Laid-Open No. 2001-0052783, an inorganic monovalent ion (for example, hexafluoroantimonate, hexafluoroarsenate, hexafluorophosphonate, perclorate, or borofluoride) and an organic acid divalent anion (for example, trifluoromethane sulfonate or naphthalene disulfonate) are used for improving the heat-resistance and the light-resistance of a diimmonium compound. However, the inorganic monovalent ion and the organic acid divalent anion may contain toxic materials such as antimony or arsenic. Further, the inorganic monovalent ion and the organic acid divalent anion are weak to moisture or heat. Thus, the diimmonium salt can be decomposed, the absorptivity of the near infrared ray can be reduced, and, on the contrary, visible ray can be absorbed. To overcome these drawbacks, in U.S. Patent Application Publication No. 2005-148786, the anion of the diimmonium compound is replaced with sulfonimide based anion. However, there is a problem that some composition including the sulfonimide based salt is hydrolyzed at high temperature and high humidity atmosphere.